What is humus?
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A dark colored amorphous substance that is highly resistant to microbial action and undergoes decomposition slowly.
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What is humus?
A dark colored amorphous substance that is highly resistant to microbial action and undergoes decomposition slowly.
How many years does it take for a climax community to be reached?
252 years.
What is the process called through which inorganic nutrients are released from humus?
Mineralisation.
What do ecological pyramids express?
Relationships at different trophic levels in terms of number, biomass, or energy.
What type of climax community is commonly reached in succession?
The mesic community.
What factors control the rate of decomposition?
Chemical composition of detritus and climatic factors.
What does the base of each ecological pyramid represent?
The producers or the first trophic level.
Does succession in water and on land lead to different climax communities?
No, it proceeds to a similar climax community – the mesic.
How does the presence of lignin and chitin in detritus affect decomposition rate?
It slows down the decomposition rate.
What does the apex of each ecological pyramid represent?
Tertiary or top-level consumers.
What happens to the amount of energy at successive trophic levels?
The amount of energy decreases.
What climatic factors are most important in regulating decomposition?
Temperature and soil moisture.
What are the three types of ecological pyramids studied?
(a) Pyramid of number; (b) Pyramid of biomass; (c) Pyramid of energy.
What is an ecosystem?
A functional unit of nature where living organisms interact among themselves and with the physical environment.
What is detritus?
Dead biomass that serves as an energy source for decomposers.
What conditions favor decomposition?
Warm and moist environments.
What does the pyramid of numbers in a grassland ecosystem illustrate?
Only three top carnivores are supported by nearly 6 million plants.
What is a limitation of ecological pyramids?
They do not account for the same species belonging to multiple trophic levels.
What are the two basic categories of ecosystems?
Terrestrial and aquatic.
What is the standing crop?
The mass of living material at a particular time in a trophic level.
What is the standing state in an ecosystem?
The amount of nutrients present in the soil at any given time.
What inhibits decomposition?
Low temperature and anaerobiosis.
What percentage of sunlight energy do primary producers convert into Net Primary Productivity (NPP)?
1%.
What does the pyramid of biomass show at higher trophic levels?
A sharp decrease in biomass.
What is the primary source of energy for ecosystems on Earth?
The Sun, except for the deep sea hydro-thermal ecosystem.
What are the two main components of the environment studied in ecosystems?
Abiotic and biotic components.
What does ecological succession refer to?
The gradual and predictable change in species composition of a given area.
What are some examples of terrestrial ecosystems?
Forest, grassland, and desert.
How is biomass measured for accuracy?
Biomass is more accurately measured in terms of dry weight.
What is nutrient cycling?
The movement of nutrient elements through various components of an ecosystem.
What must calculations of energy content, biomass, or numbers include?
All organisms at that trophic level.
What is unique about the inverted pyramid of biomass?
A small standing crop of phytoplankton supports a large standing crop of zooplankton.
What does stratification in an ecosystem refer to?
The vertical distribution of different species occupying different levels.
What percentage of incident solar radiation is photosynthetically active radiation (PAR)?
Less than 50 percent.
What is a climax community?
A community that is in near equilibrium with the environment.
What are some examples of aquatic ecosystems?
Pond, lake, wetland, river, and estuary.
What does the 10 percent law state regarding energy transfer?
Only 10 percent of energy is transferred to each trophic level from the lower level.
What are the two types of nutrient cycles?
Gaseous and sedimentary.
What does a trophic level represent?
A functional level, not a specific species.
What are the four basic components of an ecosystem?
Productivity, decomposition, energy flow, and nutrient cycling.
What do plants and photosynthetic bacteria do with solar energy?
They fix the Sun’s radiant energy to make food from simple inorganic materials.
What are sere(s)?
The entire sequence of communities that successively change in a given area.
What is biomass in an ecosystem?
Organic matter produced per unit area over time by plants during photosynthesis.
What is the biosphere regarded as by many ecologists?
A global ecosystem, composed of all local ecosystems on Earth.
What are the typical levels in a grazing food chain?
Producer, herbivore, primary carnivore, secondary carnivore.
What is another name for nutrient cycling?
Biogeochemical cycles.
What is secondary succession?
It begins in areas where natural biotic communities have been destroyed, such as abandoned farmland or burned forests.
How can a species occupy more than one trophic level?
By consuming different types of food at different levels, e.g., a sparrow as both a primary and secondary consumer.
What is an example of a simple aquatic ecosystem?
A pond.
What are seral stages?
The individual transitional communities in ecological succession.
What percentage of dry weight of organisms is constituted by carbon?
49 percent.
How is productivity expressed?
In terms of weight (g m–2) or energy (kcal m–2).
What is the significance of studying the structure of ecosystems?
To understand input (productivity), transfer of energy, and output (degradation and energy loss).
What shape is used to represent the energy relationships in ecosystems?
A pyramid shape.
Where does the reservoir for gaseous nutrient cycles exist?
In the atmosphere.
What is an ecosystem?
A structural and functional unit of nature comprising abiotic and biotic components.
Why is succession faster in secondary succession compared to primary succession?
Because some soil or sediment is already present.
What is the typical shape of pyramids of number, energy, and biomass in most ecosystems?
Upright.
What regulates the function of a pond ecosystem?
Solar input, temperature cycles, day-length, and other climatic conditions.
What are the two types of ecological succession?
Primary succession and secondary succession.
Where is the majority of global carbon found?
71 percent is found dissolved in oceans.
What are the two types of primary productivity?
Gross primary productivity (GPP) and net primary productivity (NPP).
What are man-made ecosystems?
Ecosystems such as crop fields and aquariums.
What are common detritivores in our ecosystem?
Earthworms, fungi, and some bacteria.
What are abiotic components?
Inorganic materials such as air, water, and soil.
Where is the reservoir for sedimentary nutrient cycles located?
In Earth's crust.
What are pioneer species?
Species that invade a bare area, such as lichens in primary succession on rocks.
What percentage of PAR do plants capture?
Only 2-10 percent.
Why is the pyramid of energy always upright?
Because energy is always lost as heat when flowing from one trophic level to the next.
What are the autotrophic components in a pond?
Phytoplankton, some algae, and various aquatic plants.
What is primary succession?
Succession that starts in an area with no living organisms, like bare rock.
What percentage of total global carbon is contained in the atmosphere?
About 1 percent.
What does gross primary productivity (GPP) measure?
The rate of production of organic matter during photosynthesis.
What is the major reservoir of carbon on Earth?
The atmosphere and oceans.
What regulates the rate of nutrient release into the atmosphere?
Environmental factors like soil, moisture, pH, and temperature.
What are biotic components in an ecosystem?
Producers, consumers, and decomposers.
What are the two types of plant succession based on habitat?
Hydrarch (wet areas) and xerarch (dry areas).
What is the flow of energy in an ecosystem?
Unidirectional flow from the sun to producers and then to consumers.
What paradox is observed in the pyramid of biomass in the sea?
The biomass of fishes exceeds that of phytoplankton, resulting in an inverted pyramid.
Who are the consumers in a pond ecosystem?
Zooplankton and free swimming or bottom dwelling forms.
What is secondary succession?
Succession that occurs in areas that have lost all living organisms.
How much carbon is estimated to be fixed annually in the biosphere through photosynthesis?
4 × 10^13 kg.
How is net primary productivity (NPP) calculated?
NPP = GPP - R (respiration losses).
Which has the largest population in a food chain?
Producers.
What are the two main structural features of an ecosystem?
Species composition and stratification.
Why are nutrients never lost from ecosystems?
Because they are recycled time and again indefinitely.
What is hydrarch succession?
Succession that occurs in wet areas, progressing from hydric to mesic conditions.
What are the major producers in a terrestrial ecosystem?
Herbaceous and woody plants.
What does each bar in the energy pyramid indicate?
The amount of energy present at each trophic level over a given time or annually per unit area.
What role do decomposers play in a pond ecosystem?
They break down dead matter, releasing nutrients back for reuse by autotrophs.
How long does it generally take for soil to form on bare rock?
Several hundred to several thousand years, depending on the climate.
What are some sources that release CO2 into the atmosphere?
Burning of wood, forest fires, combustion of organic matter, fossil fuel, and volcanic activity.
What relationships are created within ecosystems due to energy flows?
Cycles, chains, and webs.
What is secondary productivity?
The rate of formation of new organic matter by consumers.
What is the second trophic level in a lake?
Zooplankton.
What is primary productivity?
The rate of capture of solar energy or biomass production of producers.
What is xerarch succession?
Succession that occurs in dry areas, progressing from xeric to mesic conditions.
Who are the primary consumers?
Herbivores that feed on producers.
What role do saprophytes play in ecosystems?
They play a vital role but are not represented in ecological pyramids.
What is the movement of energy in ecosystems?
Unidirectional movement towards higher trophic levels with loss as heat.
What are ecosystem services?
Products of ecosystem processes that provide economic, environmental, and aesthetic benefits.
How do human activities affect the carbon cycle?
Rapid deforestation and massive burning of fossil fuels increase CO2 release.
What factors influence primary productivity?
Plant species, environmental factors, availability of nutrients, and photosynthetic capacity.
What are secondary producers?
Carnivores.
What is the difference between GPP and NPP?
GPP is the total production of organic matter, while NPP is the remaining biomass after utilization by producers.
What is the climax community?
A stable community that remains unchanged as long as the environment remains stable.
What are secondary consumers?
Animals that eat primary consumers.
What is primary production?
The amount of energy produced by autotrophs in an ecosystem.
What are some examples of ecosystem services provided by healthy forest ecosystems?
Purifying air and water, mitigating droughts and floods, cycling nutrients, generating fertile soils, and maintaining biodiversity.
What is a major natural reservoir of phosphorus?
Rock, in the form of phosphates.
What is detritus?
Dead plant remains and animal remains, including fecal matter, that serve as raw material for decomposition.
What percentage of photosynthetically active radiation (PAR) is in incident solar radiation?
2-10%.
What is secondary productivity?
The rate of assimilation of food energy by consumers.
How does primary succession in water progress?
From small phytoplanktons to rooted-submerged plants, rooted-floating angiosperms, and eventually to trees.
What is the beginning of the detritus food chain/web?
The death of an organism.
What is the detritus food chain (DFC) based on?
Dead organic matter.
What is the estimated annual value of ecosystem services according to researchers?
US $33 trillion.
How do plants obtain phosphorus?
Through the dissolution of phosphates in soil solution from weathered rocks.
What are the important steps in the decomposition process?
Fragmentation, leaching, catabolism, humification, and mineralisation.
What is the difference between a grazing food chain and a detritus food chain?
A grazing food chain starts with producers, while a detritus food chain starts with decomposing organic matter.
What are the three processes involved in decomposition?
Fragmentation of detritus, leaching, and catabolism.
What factors affect the species that invade during secondary succession?
Soil condition, water availability, environment, and presence of seeds or propagules.
What role do herbivores play in the ecosystem?
They are primary consumers that feed on plants.
What types of organisms are primarily involved in the DFC?
Decomposers, mainly fungi and bacteria.
How does the value of ecosystem services compare to the global gross national product (GNP)?
It is nearly twice the value of the GNP, which is US $18 trillion.
What is a key difference between the carbon and phosphorus cycles?
Atmospheric inputs of phosphorus through rainfall are much smaller than carbon inputs.
What is the role of detritivores in decomposition?
They break down detritus into smaller particles through fragmentation.
What is primary productivity?
The rate at which energy is converted by photosynthetic and chemosynthetic autotrophs to organic substances.
How does energy flow in ecosystems?
Energy flow is unidirectional, starting from plants capturing solar energy to food being transferred to decomposers.
How does the environment influence ecological succession?
Natural or human-induced disturbances can revert succession to an earlier stage and create new conditions for species.
What is a simple grazing food chain (GFC) example?
Grass → Goat → Man.
What are decomposers also known as?
Saprotrophs.
What percentage of the total cost of ecosystem services does soil formation account for?
About 50 percent.
Is there a respiratory release of phosphorus into the atmosphere?
No, unlike the carbon cycle.
What is humification?
A process during decomposition that leads to the formation of humus.
What is decomposition?
The process by which organic substances are broken down into simpler organic or inorganic matter.
What is nutrient cycling?
The storage and movement of nutrient elements through various components of the ecosystem.
How do decomposers obtain their energy?
By degrading dead organic matter or detritus.
What are the contributions of recreation and nutrient cycling to the total cost of ecosystem services?
Less than 10 percent each.
What are the components of an ecosystem?
Producers, consumers, decomposers, and abiotic factors.
What are the two types of nutrient cycling?
Gaseous and sedimentary.
What role does the detritus food chain play in aquatic ecosystems?
It is the major conduit for energy flow.
What percentage do climate regulation and habitat for wildlife each contribute to the total cost of ecosystem services?
About 6 percent each.
What are ecological pyramids?
Graphical representations showing the distribution of biomass, numbers, or energy among trophic levels.
What is ecological succession?
The sequential order of changes in a biotic community over time.
How does energy flow through the detritus food chain in terrestrial ecosystems compared to aquatic ones?
A much larger fraction of energy flows through the DFC in terrestrial ecosystems.
Why is the value of biodiversity considered difficult to determine?
Because ecosystem services are largely taken for granted as they are free.
What are the important features of a sedimentary cycle in an ecosystem?
Involves the cycling of nutrients through biological, geological, and chemical processes.
What characterizes a climax community?
It remains stable as long as the environment remains unchanged.
What connects the detritus food chain with the grazing food chain?
Some organisms of the DFC are prey to GFC animals.
What is the relationship between phosphorus cycling and ecosystems?
Phosphorus exchanges between organisms and the environment are negligible in ecosystems.
What are the salient features of carbon cycling in an ecosystem?
Involves processes like photosynthesis, respiration, and decomposition.
What is a food web?
The natural interconnection of food chains.
What is a trophic level?
A specific place in the food chain based on the source of nutrition.
What do producers, herbivores, and carnivores represent in the trophic levels?
Producers are the first level, herbivores are the second, and carnivores are the third.
